Our youth population is shrinking, but senior citizens are multiplying.

Just-released U.S. Census Bureau estimates show Merced County’s overall population has grown just 2.5 percent from 2010 to 2013.

But the numbers for those 65 and older expanded more than 11 percent during those years.

The county’s residents between the ages of 14 and 17, by contrast, declined more than 5 percent.

The story was different for those under the age of 14; their numbers grew by 2.4 percent.

The aging of Merced’s population is nothing new, and it’s happening nationwide as the post-World War II baby boomers grow old.

Merced County remains younger than much of the country, however. The median age is just 30.4 years old, compared with a national median age of 37.6 years old.

By comparison, the median age in Stanisalus County is 33.5 years old. In San Joaquin County, the median is 33.4 years.

There is a marked difference in the Sierra foothills, where Tuolumne County’s median age increased to 48.3 years and Calaveras County’s median hit 51.

Just seven states in the nation had their populations grow younger last year. Census officials think they know why that was true for North Dakota, Montana, Wyoming, South Dakota and Oklahoma.

“The population in the Great Plains energy boom states is becoming younger and more male as workers move in seeking employment in the oil and gas industry,” explained Census Bureau Director John Thompson, “while the U.S. as a whole continues to age as the youngest of the baby boom generation enters their 50s.”

Even though America as a whole is aging, it continues to be women who are living the longest.

Like most places on Earth, more boys are born in Merced than girls. The Census shows that the there were 41,059 boys under 18 in Merced County in 2013, compared with 38,848 girls.

But as people get older, women start to outnumber the men. Merced County had 14,736 women age 65 and older, compared with 12,149 men.